Due to prevalence and wide use of cellular phones, a cellular phone becomes one of the most purchased electronic items in the market. A compact ones rapidly replaces the bulky cellular phone sets, since the latter possesses some TV games in addition to the traditional communication ability. For those teenagers who are in a trend to follow the latest fashions and new tastes, the manufacturer of the cellular phones have invented a cellular phone having some parts (such as an input device or an outer casing) to be replaced with new designs by DIY means. It is noted that the input device presently used in the conventional cellular phone is replaceable. However, the replacing operation is somewhat difficult and includes several complicated steps. In case of an accidental fall from the user's hand, the input device disengages easily from the main body of the conventional cellular phone.
FIG. 1 shows an exploded and perspective view of a conventional input device 1 to include a casing 10, a flexible membrane 11, and a printed circuit plate 12.
The casing 10 has a coupling face 101 and a periphery confining the coupling face 101. The casing 10 further has a plurality of through holes 102 formed through the coupling face 101 and a plurality of retention recess 103 surrounding the holes 102. The flexible membrane 11 has a plurality of input keys 111, a periphery confining the input keys 111, and a plurality of inserts 112 extending outwardly from the periphery. Once the flexible membrane 11 is coupled to the coupling face 101 of the casing 10, the inserts 112 extend respectively into the retention recess 103 of the casing 10, thereby preventing disengagement of the flexible membrane 11 from the casing 10. The printed circuit plate 12 is disposed within the casing 10 below the coupling face 101 thereof, and has a plurality of actuators 121 extending respectively through the holes 102 on the coupling face 101 to make contact with the input keys 111 of the flexible membrane 11. Under this condition, pressing of one of the input keys 111 will result in depression of the respective actuator 121, which, in turn, results in a data input operation.
FIG. 2 shows a sectional view of another conventional input device 20 used in a cellular phone. As shown, the conventional input device 20 includes a flexible membrane 201 having a plurality of inserts 202 extending respectively into the retention recesses 206 of the casing, and a plurality of lower projections 203 in contact with the actuators 204 of the printed circuit board 205 disposed within the casing below the flexible membrane 201. Pressing of the flexible membrane 201 will result in depression of the lower projection 203 against the actuator 204, which, in turn, results in a data input operation.
Though the aforesaid input device allows users to replace different flexible membranes, the flexible membrane may easily disengage the casing in case of an accidental fall since the inserts 112, 202 are not retained within the retention recesses 103, 206 of the casing in a tight-fit manner. No other fastening device is employed in the conventional input device in order to prevent untimely removal of the flexible membrane from the casing.